Modified polymers useful in photographic elements



United States Patent 3,392,151 MODIFIED POLYMERS USEFUL IN PHOTOGRAPHIC ELEMENTS Louis M. Minsk and Edward P. Abel, Rochester, N.Y., as-

signors to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey No Drawing. Original application Dec. 21, 1964, Ser. No. 420,203, now Patent No. 3,316,097, dated Apr. 25, 1967. Divided and this application Dec. 27, 1966, Ser. No. 619,104

2 Claims. (Cl. 260-775) This is a division of application Ser. No. 420,203 filed Dec. 21, 1964, now U.S. Patent No. 3,316,097.

This invention relates to gelatin-silver halide emulsions, and more particularly to gelatin-silver halide emulsions having increased covering power of developed silver, and to the process for preparing such elements.

The maximum optical density of a silver image of a photographic film after exposure, processing and drying, and hence the covering power, appears to depend not only upon the amount of silver which results from the development process, but also upon the way in which the silver is laid down in the photographic element during processing and the stresses to which it is subjected in the drying step. The term covering power as used herein refers to the ratio of the optical density of developed silver to the actual quantity of silver.

The intimate structure and density of the silver deposit produced by the reduction of silver halide to metallic silver is influenced during processing and drying by the vehicle in which the silver halide grains are suspended. It therefore appears desirable to modify the vehicle in some manner whereby the covering power of developed silver is increased, thereby providing an increase of maximum density, an increase in gamma and very often an increase in speed. It is, of course, desirable that the modification of the vehicle does not interfere wtih other photographic properties of the emulsion.

It is one object of our invention to provide gelatin photographic emulsions which exhibit an increase in covering power of developed silver. Another object of our invention is to prepare photographic emulsions having an increase in covering power of developed silver, which emulsions are not adversely affected in their other sensitometric characteristics, such as density, resolution and acutance. Other objects of our invention will appear herein.

These and other objects of our invention are accomplished by incorporating in gelatin silver halide emulsions a polymer containing repeating units having the following formula:

CH2(l3 H o o 43-NH-R1 wherein R is a carbon chain of from 1 to 5 carbon atoms substituted with from 1 to 3 substituents having the formula -COXR R X being selected from the group consisting of Formula 1 mer containing repeating units having the following formula:

Formula2 CH2-CH- o o o C--NH(CHz)nCNHOH2CHzOH wherein n is an integer from 1 to 5. We have found that gelatin silver halide emulsions containing polymers having these repeating units exhibit an increase in covering power of developed silver, which results in an increase of maximum density, gamma and very often an increase in speed. We have also found that the sensitometric characteristics of the emulsion are not adversely affected by the subject polymers.

We have further found that the covering power of developed silver may be increased with copolymers having repeating units as defined by Formulas 1 and 2 above with other monomers, such as vinyl alcohol and other vinyl monomers including those represented by the following formula: Formula 3 [-0 Hull 13-] oxy; an amide including N-alkyl and N,N-dialkyl amides wherein the alkyl groups contain 1 to 5 carbon atoms,

such as methyl, ethyl, propyl, butyl or amyl; or a carbamate group such as OCONHR COOR wherein R and R each are carbon chains of 1 to 5 carbon atoms,

preferably alkylene.

The polymers and copolymers which may be employed to increase the covering power of developed silver of gelatin silver halide emulsions in accordance with our invention may be prepared in any convenient manner such as by treating the reaction product of poly(vinyl alcohol) and an ester of isocyanato monoor polybasic fatty acid with an amine. The reaction of the isocyanato compound with the poly(vinyl alcohol) may be partial or complete, as may be the reaction of the amine with the initial reaction product. The preparation of the polymers and copolymers employed in accordance with our invention is illustrated in Examples 1-6.

Example 1.The preparation of poly(vinyl p-hydroxyethylcarbamylmethylcarbamate) mole percent reaction) In a 5-liter flask equipped with a stirrer, thermometer, reflux condenser with calcium chloride tube, and a dropping funnel were placed 2160 ml. of pyridine and 264 g. of low-viscosity poly(vinyl alcohol) that had been dried overnight in a 50 air oven. The stirred suspension was heated to C. in a Glas Col mantle and 542 g. of ethyl isocyanato acetate were added dropwise at the rate of approximately 5-6 drops/second. Within 5-10 minutes after the start of the addition, the slurry began to clear and the viscosity increased. As the heating and stirring were continued, the viscous dope usually became gelatinous, yet soft enough to allow some mixing. After 25 minutes, the addition of the ethyl isocyanatoacetate had been completed. The temperature of the reaction mixture was 119 C. Heating was continued for /2 hour with the temperature dropping spontaneously to C. After 802 g. of ethanolamine had been added through the dropping funnel over a /z-hour period, 480 'ml. of distilled water were added slowly. The reddish-colored gel began to break apart and in minutes a smooth, homogeneous dope was obtained. Heating and stirring were continued for 4 and /2 hours at 90l00 C. The dope was cooled to 60 C. and 'precipitated by pouring into stirred isopropyl alcohol. The soft, yellowish poly- J 3 rner,..after being allowed to soak overnight in fresh isopropyl alcohol, was washed for /2 hour, with decantation after each wash, a total of 7 times. The soft polymer hardened on Washing and broke up intosmall granular pieces. The solid was dissolved in the mill by the addition of 1 and /2 liters of water to obtain a viscous, bright, yellow dope of pH 9.40. The dope was treated with a sufiicient quantity of Amberlite IR-120 ion exchange resin to reduce the pH to 2.32.

A sample of this acidic dope was isolated in isopropyl alcohol for analysis. The main portion of the dope was adjusted to a pH of 6.20 with NaOH. The yield was 565 grams dry weight.

Example 2.The preparation of poly(vinyl B-hyd-roxyethylcarbamylmethylcarbamate) In a 2-liter flask equipped with a stirrer, thermometer, reflux condenser with calcium chloride tube, and a droping funnel were placed 1080 ml. of pyridine and 3 moles 132 g. of low-viscosity poly (vinyl alcohol) that had been dried overnight in a 50 C. air oven. The stirred suspension was heated to 92 C. in a Glas Col mantle and 2.1 moles (70 mole ercent272 g.) of ethyl isocyanatoacetate were added dropwise over a A-hour period. The temperature of the dope rose to 115 C. Heating was continued for /2 hour while the temperature dropped spontaneously to 107 C. External cooling lowered the temperature to 90 C. and the polymer was isolated by pouring the dope into distilled water. The soft, yellow solid was washed a total of 6 times in a one-quart W.P. mill with fresh changes of distilled water. A sample of the polymer was redissolved in acetone, reprecipitated in ethyl acetate and dried under vacuum at room temperature. The nitrogen content was found to 'be 5.9 percent, which indicated that the intermediate contained 73 weight percent of combined vinyl carbethoxymethylcarbamate.

The damp solid, amounting to 500 g., was placed in a 2-liter bottle containing 300 g. of aminoethanol. The bottle was sealed and tumbled for several days at room temperature until a viscous yellow dope was obtained. The polymer was isolated by pouring the dope into stirred ethyl acetate. The soft yellow solid was washed by kneading in several changes of fresh ethyl acetate and then taken up in 500 ml. of distilled water. The aqueous solution of polymer was treated with a sufiicient quant ity of Amberlite IR-120 ion exchange resin to reduce the pH of the dope to 2.70. A sample of this dope was isolated for analysis by precipitation in ethyl acetate and drying in a vacuum oven of 35-40 C. The nitrogen content was found to be 10.35 percent, equivalent to 60 weight percent of combined vinyl fi-hydroxyethylcarbamylmethylcarbamate; the ethoxyl content was 3.0 percent, equivalent to 11.5 weight percent of combined unreacted vinyl carbethoxymethylcarbamate, and a carboxyl equal to 0.34 ml. N NaOH/g., equivalent to 4.85 weight percent of combined vinyl carboxymethylcarbamate. This leaves 23.65 weight percent of combined vinyl alcohol in the polymer.

The main portion of the dope was adjusted to a pH of 6.0 with dilute NaOH. The yield was 268 g. dry weight.

Example 3.The preparation of poly(vinyl fi-hydroxyethylcarbamylmethylcarbamate) (70 mole percent reaction from butyl isocyanatoacetate) In a 2-liter flask equipped with a stirrer, thermometer, reflux condenser with calcium chloride tube, and a dropping funnel were placed 720 'ml. of pyridine and 88 g. of poly(vinyl alcohol) that had been dried overnight in a 50 C. air oven. The stirred suspension was heated to 93 C. in a Glas Col mantle and 220 :g. of butyl isocyanatoacetate were added dropwise. Within 10 minutes the slurry began to clear and the viscosity increased. Short-ly thereafter the viscosity decreased and a smooth, homogeneous dope was obtained. The addition of the butyl isocyanatoacetate required /3 hour. Heating and stirring were continued for 2 hourswhile the tempera? of 6 times. The polymer hardened on washing and broke up into small granular pieces. The solid was dissolved in the mill by adding 500 ml. of distilled water. The basic dope was treated with a sufficient quantity of Amberlite ion exchange resin (IR-) to reduce the pH to 1.75. A sample of the dope was isolated by precipitation in isopropyl alcohol for analysis. The main portion of the dope was adjusted to a pH of 6.0 with alkali. The yield Was 206 g. (dry weight).

Example 4.The preparation of poly(vinyl 1,2-bis[,3-hydroxy ethylcarbamyl]ethyloarbamate) In a one-liter flask equipped with a stirrer, thermometer, reflux condenser with calcium chloride tube, and a dropping funnel were placed ml. of pyridine and 22 g. of low-viscosity poly( vinyl alcohol). The stirred suspension was heated to 99 C. in a Glas Col mantle and 134 g. of diethyl ot-isocy-anatosuccinate were added dropwise. A clear, dark amber dope was obtained while the temperature rose to 119 C. Heating was continued for 2 hours. The polymer was isolated by pouring the dope into distilled water and washed by kneading in fresh distilled water several times. The damp polymer was placed in a bottle containing 600 ml. of ethanolamine and tumbled at room temperature for several days until a viscous, reddish-colored dope was obtained. The polymer was isolated by pouring the dope into stirred isopropyl alcohol and washed several times in fresh isopropyl alcohol to remove the major portion of the residual ethanolamine. Two hundred milliliters of distilled water were added to dissolve the polymers, and the aqueous solution was treated with a sufficient quantity'of Amberlite IR-120 ion exchange resin to reduce the pH to 2.60. A sample of this dope was isolated for analysis by precipitation in isopropyl alcohol and drying in a vacuum oven at 3540 C. The isolated sample was found to contain 11.4 percent nitro-. gen, equivalent to 63.5 weight percent of combined vinyl 1,2 (dihydroxyethylcarbamido)ethylcarbam-ate; 7.5 percent ethoxyl, equivalent to 21.6 weight percent of combined unreacted vinyl 1,2-(dicarbethoxy)ethylcarbamate, and a carboxyl equal to 0.73 ml. N NaOH g., equivalent to 14.7 weight percent of combined vinyl 1,2-(dicarboxy) ethylcarbamate. The main portion of the dope was adjusted to a pH of 6.20 with dilute NaOH using a Beck man Model G pH meter. The yield was 89 g. dry weight.

Example 5.The preparation of poly (vinyl 1,3-bis[;9-hydroxyethylcarbamyl]-propylcarbamate) (100 mole percent reaction) In a ZOO-ml. flask equipped with a stirrer, thermometer, refiux condenser with calcium chloride tube, and a dropping funnel were placed 72 ml. of pyridine and 8.8 g. of low-viscosity poly (=vinyl alcohol) that had been dried overnight in a 50 C. air oven. The stirred suspension was heated to 90 C. in a Glas Col mantle and 46 g. of diethyl m-isocyanatoglutarate were added dropwise. The addition required A hour. At this time a smooth, dark amber dope had been obtained and the temperature had reached 113.5 C. Heatingwas continued for 2% hours while the temperature dropped spontaneously to 98 C. The dope was poured slowly into distilled water to pre: cipitate a soft, light-yellow polymer. After washing the soft cake in water several times, it was dissolved in acetone and reprecipitated by again pouring into stirred water slowly. The soft cake was washed by kneading in distilled water and dried in a vacuum oven at 4045 C carbamate, ester carbamate, carboxy carbamate and vinyl a cohol. The polymers obtained in these examples and Examples 1-6 are described in Table 1.

TABLE I Wt. Percent Calculated from Analyses Preparation Reference Alkanol Unreacted Oar-boxy Vinyl Akohol R-NCO R-NH Amide Ester Carbamate (by difierence) Carbamate Carbamate Example 7 Ethyl isocyanato acetate 2-amin0ethanol..- 75. 2 6. 1 18. 7

d .d 60. 5 11. 5 4. 85 23. do 80. 0 10. 0 4 0 6. 0 do 40. 0 29. 6 3 34 27. 06 do- 42. 0 32. 5 3 04 22. 46 Butyl isocyanato-acetate. .d0 69. 7 4. 06 Example 5 Diethyl a-isocyanatoglutarate do 44. 7 36. 4 6. 1 12. 8 Example 4 Diethyl misoeyanatosuccinate do 63. 5 21. 6 14. 7 Example 6 Ethyl isocyanato-acetate Iminodiethanol 46. 2 28. 0 9. 0 16. 8

The polymers obtained in Examples 1-9 were tested for their ability to increase the covering power of developed silver by incorporating the polymers in a standard sulfur-gold sensitized high speed coarse-grain silver bromoiodide emulsion of the type commonly used in medical X-ray films. Each emulsion sample was coated on a cellulose acetate support at a coverage of 560 mg. of silver and 900 mg. of gelatin per square foot. A sample of each coating was exposed on an Eastman 1B Sensitometer and processed for 3 minutes in Kodak Developer D-19B. The results obtained with the polymers of Examples 1, 2, 8, and 9 were sufliciently similar to the results obtained with emulsions containing the polymer contained in Example 7 that the photographic results thereof have not been separately listed. The improvement in increased covering power of developed silver in emulsions in accordance with the invention is demonstrated by the photographic results set out in Table 11.

TABLE II The polymer was placed in a bottle with 300 g. of ethanolamine and 50 ml. of water and tumbled at room temperature for several days until a viscous amber dope was obtained. The polymer was isolated by pouring into stirred acetone and washed several times in fresh acetone to remove the major portion of the residual ethanolamine. Water was added to dissolve the polymer, and the aqueous solution was treated with a sufficient quantity of Amberlite 1R-120 ion exchange resin to reduce the pH to 2.30. A sample of this acidic dope was isolated for analysis. The main portion of the dope was adjusted to a pH of 6.55 with aqueous NaOH. The yield was 28.8 g. dry Weight.

The acidified polymer analyzed for the following: N- 8.6/8.3; ethoxyl12.0; titration-0.28 ml. N NaOH/g. polymer.

Example 6.-The preparation of poly(vinyl bis[B-hydroxyethyl] -carbamylmethylcarbamate) In a 500-ml. flask were placed 200 ml. of iminodiethanol, 20 ml. of distilled water, and 43 g. of poly(viny1 Concentration Relative carbethoxymethylcarbamate) intermediated prepared as in Polymer per %g speed Gamma Fog Example Th3 Il'llXtllTfl was heated n a t a bath with C t l 100 L84 114 1 70 gentle stirring for approximately 24 hours, during which 43 123 2.40 0. 05 2.10 time a clear, reddish dope had been obtained. The polyggggg "g5 gig 8:82 23 mer was isolated by pouring the dope into stirred isopropyl ample 6 60 123 2.80 0.06 2. 25 alcohol- The soft yellvw solid was kneaded y hand ififiigia'sifij at 13% 212% 3132 i3; eral times in fresh isopropyl alcohol and then taken up in Ex mple 3 60 132 2.06 0.07 2: 10 100 ml. of distilled water. The aqueous solution was tre-at- 45 Exa m p16 10 ed with a sufiicient quantity of Amberlite IR-120 ion exchange resin to reduce the pH to 2.70. A sample of this dope was isolated for analysis by precipitation in isopropyl alcohol and drying in a vacuum oven at 35-40 C. The isolated sample was found to contain 8.7 percent nitrogen, equivalent to 46.2 weight percent of combined vinyl bis(fi-hydroxyethyl)carbamylmethylcarbamate; 7.3 percent etboxyl, equivalent to 28 weight percent of combined unreacted vinyl carbethoxymethylcarbamate, and TABLE III a carboxyl equal to 0.62 ml. N NaOH/ g. equivalent to r Concentration Relative 9.0 weight percent of combined vinylcarboxymethylcar- Polymer figf Speed Gamma Fog bamate. This leaves 17 percent of combined vinyl alcohol Contr 1 m0 1 n the polymer. The mam portion of the dope was adg 123 Mg 8189 mg usted to pH of 6.10 with dilute NaOH. The yield was 33 dry Weight Examples 11-18 A number of polymers were made in accordance with the method described in Examples 1-6. The principal The procedure of Example 1 was followed to obtain reactants are described in Table IV, together with a depolymers containing varying amounts of alkanol amide scription of the content of the polymers obtained.

ADDITIONAL POLYMERS Examples 7-9 Wt. Percent Example Preparation No. Alkanol Unreacted Carboxy Vinyl R-N C O R-NHz Amide Ester Oarbamate Alcohol Carbamate Carbamate (by difierence) 1 1 Ethyl isoeyanatoacetate 3-aminopropanol 0. 7 12 do Isopropylamine 48. 1 11. 4 13 do 2-methoxyethylamin 61 29 14 do Zethoxy-ethylamine 56. 6 34. 1 15 (in 2-amino2-methyl-1-propanol 35 18 16 do 2-amino-2-ethyl-1,3-propanediol 64 36 17." rln 2-amino-2-hydroxy-methyl-l,3- 67 26. 0

propanediol. 18 do 2-amineoethanol 52. 7 11. 4

r The polymers obtained in Examples 11-18 were incorporated in emulsions and tested as described above. The results obtained show that each of the polymers increased the covering power scribed in Table V. w

TABLE V Polymer Cone, g./Ag Rel. Gamma Fog Y mole Speed 1 Example 11 45 126 1. 48 .14 Example 11. 100 1.18 14 Example 12 30 102 1. 68 13 Example l2.. 0 100 1. 45 .12 Example 13"--- 45 123 1. 48 11 Example 13 0 100 1. 10 Example 14 '97 1. 60 13 Example 14"--- 0 100 1. 47 14 Example 15 102 1. 10 0 100 1. 38 10 45 112 1. 08 0 100 1. 27 10 45 118 1. 48 13 0 100 1. 27 15 '45 115 1. 60 14 Example 18... 0 100 1 v1.25 13 As indicated heretofore, our invention relates both to the use of homopolymers and copolymers containing carbamylated repeating units. The most useful polymers in accordance with the invention contain from 30 to 100, and preferably 50 to percent by weight of repeating units as defined in Formulas 1 or 2 above, the remainder of the polymer being composed of repeating units in accordance with Formula 3 above. The most important feature of the polymers of the invention is the combined alkanol amide carbamate. 4

The polymers and copolymers of our invention are incorporated in gelatin silver halide emulsions at a ratio of about 10 to 75 grams per mole of silver and from 5 to 50 percent by weight of the gelatin employed in the emulsion. i

Particularly useful results are obtained when the poly mers of the invention are incorporated in X-ray emulsions, which may be used, for example, in X-ray elements of the type having integral intensifying screens, such as those described in Kennard et al. US. patent application Serial No. 223,377, filed September 13, 1962, now abandoned in favor of continuation applications Serial Nos. 364,244, filed May 1, 1964, now US. Patent No. 3,300,311, and 364,245, filed May 1, 1964, now US. Patent No. 3,300,310. i

The gelatin silver halide emulsions of our invention may contain various chemical sensitizers, stabilizers, speed-increasing compounds, coating aids, and gelatin hardeners and plasticizers, such as those described in US. Patent 3,039,673.

of developed silver,,as de- 8 l The molecular weight of the polymers which we employ in our invention may vary over a wide range; the most useful molecular weights are such as would be derived from a poly(vinyl alcohol) of inherent viscosity from 0.10 to 0.90, and preferably from 0.30 to 0.50. The inherent viscosity is measured in water at a concentration of 0.25 g. per m1. of solution at 25 C.

The invention has been described in detail with particular reference to preferred embodiments thereof but it will be understood that variations and modifications can be efiected within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

We claim:

1. A polymer containing repeating units having the following formula:

wherein 'R is a carbon chain of from 1 to 5 carbon atoms substituted with from 1 to 3 substituents having the formula COXR R X being selected from the group consisting of and lTIN R being selected from the group consisting of hydrogen and alkyl groups of 1 to 5 carbon atoms, and R and R each are selected from the group consisting of hydrogen; alkyl groups of 1 to 5 carbon atoms; alkoxy substituted alkyl groups having 1 to 5' carbon atoms and hydroxy substituted alkyl groups of from 1 to 5 carbon atoms.

2. Poly(vinyl fl hydroi'ryethylcarbamylmethylcarbamate).

References Cited UNITED STATES PATENTS 2,727,020 12/1955 Melamed et a1 26080.3 2,887,469 5/ 1959 Unruh et a1 26077.5 2,948,611 8/ 1960 Barney 9635 3,147,116 9/1964 Roth 9635 3,316,097 4/1967 Minsk et al. 96-114 FOREIGN PATENTS 667,195 7/ 1963 Canada. 909,061 10/ 1962 Great Britain.

DONALD E. CZAJA, Primary Examiner.

F. MCKELVEY, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,392,151 July 9, 1968 Louis M. Minsk et a1.

It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, line 52, after "50" insert C. Columns 5 an 6, before "ADDITIONAL POLYMERS" insert TABLE IV Column 7, line 51, "3,039,673" should read 3,039,873

Signed and sealed this 10th day of February 1970.

(SEAL) Attest:

WILLIAM E. SCHUYLER, JR.

Commissioner of Patents Edward M. Fletcher, Jr.

Attesting Officer 

